As the use of touch screens, such as for public information kiosks, portable devices, and gaming applications and the like, increases, so does the need for efficient processes for manufacturing reliable touch screens. Typically, touch screens, and in particular capacitive touch screens, are manufactured via a multi-step process that includes multiple high temperature curing stages. For example, a touch screen may be manufactured by first washing a piece of flat glass, screen masking the glass surface where no conductive coating is desired and coating the glass surface with a transparent conductive coating, such as antimony tin oxide (ATO). The transparent conductive coating is then often fired at a high temperature of about 510 degrees Celsius or higher to improve properties thereof. The coated glass substrate is then washed and a conductive electrode, such as a silver conductive epoxy or paste portion, is printed onto the surface and then this is cured at a high temperature, such as about 480 degrees Celsius or higher. The glass is washed again and a hardcoat layer (such as an inorganic oxide, such as silicon dioxide) may be coated, such as by spraying, onto the glass, or the glass may be dipped into a precursor solution of the hardcoat coating. The hardcoat is then cured at a high temperature, such as about 520 degrees Celsius or thereabouts. A protective border layer may then be screened over the silver and may then be cured, such as via an ultraviolet (UV) curing process or, where a glass frit may be used, via another high temperature firing process. The glass is then cut to its final size and the edges are seamed before the touch screen is washed and packaged for shipping. The conductive coating is preferably antimony tin oxide due to the stability and uniformity of ATO during the multiple heat curing processes. Examples of such coatings and sensors or touch screens are described in U.S. Pat. Nos. 6,488,981; 6,549,193; 6,727,895; and 6,842,171, which are hereby incorporated herein by reference in their entireties.
Although it has been proposed to form a transparent conductive layer or coating of an indium tin oxide (ITO) material, commercial success of such a touch screen has been limited due to the difficulties in achieving substantially uniform resistivity of the conductive coating across the sheet. Also, because ITO has the propensity to reduce or change its electrical properties when exposed to high temperatures as formed, such a coating has heretofore been not preferred for use in such touch screen applications that require multiple high temperature firings. Also, due to the higher specific conductivity of ITO relative to ATO, a substantially thinner coating of ITO is needed to achieve the resistance desired for such touch screens or panels. If the ITO coating is degraded to have a reduced conductivity, uniformity concerns with the material arise.